1. Field of the Invention
The present invention relates to Venetian blinds and, more particularly, to a mechanism for tilting and raising and lowering such blinds.
2. Description of the Prior Art
Venetian blinds, once popular forty or fifty years ago, are now coming back into use in custom installations. Most often the blinds are used in homes in the medium to upper price brackets and in offices and institutions after having been substantially displaced by other sunshading and privacy devices.
Normally, Venetian blinds comprise a plurality of slats or louvers supported, at least toward the opposite ends of the slats, by so-called ladders comprising a pair of angle or tilt control strings located on opposite sides of the slats and a lift string extending vertically through the center of the slats. Extending generally horizontally between the tilt strings and spaced vertically in accordance with the width of the slats, are a series of cross strings or tapes which serve to support the respective slats in an appropriately spaced relationship. Each slat is, of course, provided with a central opening through which the lift string extends. The opening is elongated in the transverse direction of the slat in order to permit the slats to be tilted through a substantial angle to permit opening and closing the blind without interference between the slats and the lift strings.
By varying the vertical position of the tilt strings of a single ladder with respect to each other--and thereby the angles of the cross tapes extending between them--the slats are rotated in unison, thereby opening and closing the blind. The blind may be lifted entirely to the top of the associated window or other space where it is installed by causing the lift string to be pulled upwardly, as over a pulley arrangement in the head piece of the blind, thereby lifting the bottom rail of the blind and pulling all of the slats up with it as the slack is taken up in the lift string. It can be readily seen that the mechanisms for raising and lowering, as well as the mechanism for tilting the slats, normally contained in the headrail, must be designed in a manner to function effectively and yet be compact and simple.
Moore in U.S. Pat. No. 1,949,653 and Cooper in U.S. Pat. No. 2,003,174 disclose arrangements for controlling the angle of the tilt in the Venetian blind slats. These two arrangements are typical of the type in which a tilt rail is supported below the headrail and controlled so as to vary the tilt of the slats suspended from the tilt rail. U.S. Pat. No. 2,017,541 of Kuyper and U.S. Pat. No. 2,223,633 of McKerlie disclose another conventional means of constructing Venetian blinds in which the upper ends of each ladder are wound around rods in opposite directions. Thus the rotation of both rods in one direction causes tilting of the slats.
Randmark in U.S. Pat. No. 3,100,013 and Fountain in U.S. Pat. No. 3,294,153 both disclose the concept of utilizing horizontal top-mounted bars attached to the tilt strings. In Randmark, the mechanism is a flexible band or tape which can be reciprocated in response to pull strings. In Fountain, on the other hand, the bars move in opposite directions with a pulley being provided to transmit tension from one bar to the other.
Numerous other prior art mechanisms are known; for instance, see Krueger U.S. Pat. No. 1,063,042; Walker et al U.S. Pat. No. 2,687,770; Walker U.S. Pat. No. 2,582,301; Agee U.S. Pat. No. 1,845,574; and Zubiria U.S. Pat. No. 2,158,454. None of these systems, insofar as can be determined, deals with the problem solved by the present invention.